1. Field of the Invention
The present invention relates to a wireless communication system and a method for wireless communication, or more particularly, to a cellular wireless communication system including small-scale base stations (for example, femto cell base stations) and a method for a cellular wireless communication.
2. Description of the Related Art
In cellular wireless communication systems for cellular portable phones or the like, a macro cell method in which one base station covers a wide area has been employed in the past. The macro cell method features its adaptability to high-speed movement due to a low handover frequency and its capability to expand an area using a small number of base stations. However, the macro cell method finds it hard to cope with a dead zone created indoors or locally.
In contrast, an approach to elimination of the dead zone by installing a base station, which provides a cell smaller than a macro cell, in a place where radio waves from a macro cell base station are hard to reach has been conceived.
In particular, a femto cell method in which a small-scale base station capable of covering, for example, one house is installed in each household is attracting attention these days. In a so-called third-generation cellular wireless communication system employing the Wideband Code Division Multiple Access (W-CDMA) or Evolution Data Optimized (EV-DO), provision of commercial services according to the femto cell method is beginning.
In addition, for the Long Term Evolution (LTE) that is the standard succeeding W-CDMA, specifications for the femto cell method are formulated.
In the femto cell method, a small-scale base station (femto cell base station) that covers a radio-wave propagation range nearly identical to the range covered by a wireless LAN is installed in each household or building, and the femto cell base station is connected onto a cellular communication network over the Internet. For the purpose of eliminating the dead zone, the femto cell base station may be used in such a manner that a femto cell locally overlaps a macro cell. A frequency band employed by the femto cell base station is identical to or overlaps a frequency band employed by a macro cell base station.